岩土工程技术

2022, 36(4): 1-3.

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Abstract:

2022, 36(4): 1-1.

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Research Progress on Application of Cement Soil Mixing Pile in Gravel Stratum

Liang Tao, Zhong Jianwen, Guan Yanpeng, Liu Xiaoli, Gao Yanwei

2022, 36(4): 259-266. doi: 10.3969/j.issn.1007-2993.2022.04.001

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Gravel stratum has low compressibility and high shear strength. There are some technical problems in the application of cement soil mixing pile method in gravel stratum. The application of cement soil mixing pile in gravel stratum was summarized, and the technical difficulties and main improvement measures of cement soil mixing pile in gravel stratum were also discussed. The action mechanism, applicability, advantages and disadvantages of each improvement method were analyzed. During the process of cement soil mixing pile crossing gravel stratum, there are technical problems such as low construction efficiency, large wear of drilling tools and difficult control of construction quality. At present, there are successful cases of cement soil mixing pile applied to gravel stratum. The main improved processes can be divided into three types, including drilling, mixing and slag discharge, which can be subdivided into improving the power of power machine head, controlling the bit weight and speed, improving the strength of drilling tool materials, improving the structural form of bit and mixing blade, and using soil modifier. If necessary, pilot hole replacement and impact crushing can be introduced to assist the construction. However, in the successful cases, the particle size and thickness of gravel stratum are small, generally no more than 150 mm in particle size, and there is no systematic matching method between gravel stratum characteristics and mechanical equipment technical parameters. The research on the interaction mechanism between mixing pile equipment and gravel stratum needs to be deepened.

Stress Analysis of Contact Surface Between Tunnel Structure and Soil in Yellow Clay Area

Zhao Jiangtao

2022, 36(4): 267-270. doi: 10.3969/j.issn.1007-2993.2022.04.002

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In order to study the mechanical properties of the interface between tunnel support structure and surrounding rock in yellow clay area, the basic mechanical test and three-dimensional numerical simulation of the contact surface were carried out, and the development law of the stress and deformation of the contact surface was summarized and analyzed. On this basis, the damage mechanical constitutive model of the contact surface between tunnel support structure and surrounding rock soil in yellow clay area was proposed. The constitutive model is practical and can provide theoretical support for similar projects in yellow clay area.

Upper Bound Analysis and Application for Shield Supporting Pressure in Vertical Layered Soil Stratum

Jin Cheng, Wu Fan, Sun Qianwei, Gong Qiuming, Han Peng

2022, 36(4): 271-277. doi: 10.3969/j.issn.1007-2993.2022.04.003

[Abstract](102) [FullText HTML] (32) [PDF 1555KB](21)

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In order to determine the shield supporting pressure for subway tunnel face in vertical layered soil stratum, based on wedge failure mode, the calculation formula of supporting pressure was derived by upper bound method of limit analysis. Under certain constraints, the optimal solution of supporting pressure was got by using MATLAB to write particle swarm optimization. The validity of the proposed solution was demonstrated by comparing the calculated results with existing literature research. The influence of various parameters on supporting pressure was analyzed. The results show that the supporting pressure decreases with the increase of soil strength. With the increase of tunnel depth ratio, supporting pressure increases first and then becomes stable. When the internal friction angle of upper soil is larger than that of the lower soil, the calculation result of considering layering is larger than that of not considering layering. Taking the Huai-Fu section of Shenzhen Metro Line 12 as an example, the theoretical calculation value of supporting pressure matches well with the measured value of earth pressure. Under the earth pressure, the EPB is tunneling stably. The upper bound method of supporting pressure can be applied in practical engineering.

Simulation Analysis on the Evolution Process of Rainfall-induced Landslide Under Dry-wet Conditions

Zhou Yingbo, Chai Shaobo, Zhou Qiupeng, Duan Zhiqiang, Wang Jin

2022, 36(4): 278-283. doi: 10.3969/j.issn.1007-2993.2022.04.004

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The geological hazards of rainfall-induced accumulation slope are very common in south of China. It is of great theoretical and practical significance to reveal the law of instability evolution for the monitoring and early warning of soil landslide in mountainous and hilly areas of China. Based on the generalized model of typical geological landslides and rainfall model of rainfall induced landslide in western Hubei area, combined the Geo-Studio software, the evolution process of the slope destabilizing were discussed from the aspects of seepage field, stress field and displacement field of wet and dry conditions. Compared with the slope that has not experienced long-term drought, the long-term drought can make rainfall infiltrate deeper into the slope, the variation range of matrix suction is larger, and the soil displacement in the slope caused by rainfall is larger at the same time. Under drought conditions, it is obvious that the plastic zone with large area is distributed along the slope foot, and the slope is more likely to fail and fail eventually. The research results play a positive role in promoting the theoretical development of the prevention and control of landslide geological hazards in western Hubei province.

Solutions and Measures for TBM Extrication in Extremely Weak and Broken Water Rich Formation

Li Xiaobin

2022, 36(4): 284-288. doi: 10.3969/j.issn.1007-2993.2022.04.005

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When the horizontal pilot tunnel TBM of a railway tunnel project passes through the weak, broken and water rich stratum, it burst and collapsed. In the process of geological exploration and pipe shed construction, abnormal conditions occurred, such as excessive drilling pressure, mud wrapped drilling, water gushing in the hole and so on. Water poured suddenly and large amount of sediments gushed in the left side of shield tail, which caused the deformation of shield body and main beam area surrounding rock. TBM was trapped and had great risk. In order to deal with the problems and make TBM out of trouble quickly, the methods of advanced drilling, grouting reinforcement, high level adit drainage, installation of double speed reducer, advanced pipe shed support and shield surrounding excavation were adopted, and finally the TBM is out of trouble. The combined methods provides a reliable reference scheme for the construction and danger treatment of TBM in extremely weak and broken water rich strata.

Coast Construction of Large Diameter Open Steel Pipe Pile Driving Analysis and Bearing Properties Research

Zhang Zhaobin, Zhang Kaiwei, Zhao Haichao, Liu Qingyu, Zhou Shihao

2022, 36(4): 289-294. doi: 10.3969/j.issn.1007-2993.2022.04.006

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Large diameter open steel pipe pile is proposed to be used for the foundation pile of a power plant wharf project. In order to obtain the design and construction parameters of engineering pile, the pre-construction test pile was carried out. During the test, the stress and deformation characteristics of steel pipe piles at different ages are comprehensively tested and analyzed by means of high strain dynamic test, static load test pile internal force test and so on. The results of pile test research are as follows: (1) The bearing type of test pile is determined as friction pile by counting the proportion of end resistance; (2) By observing the difference of soil surface inside and outside the pile pipe and combining the characteristics of end resistance deformation curve, it is determined that the test pile has pile end clogging effect; (3) The static load internal force test shows that with the continuous increase of load, the exertion degree of end resistance increases rapidly step by step, the soft weakening area of friction resistance appears in the section of 0~12 m, and the whole loading process of other sections shows an enhanced state; (4) The prediction formula of the final bearing capacity of steel pipe pile is obtained by synthesizing the relationship curve between the number of blows and bearing capacity and the relationship curve between age and soil recovery coefficient of the upper 3 m pile.

Quantitative Analysis of the Maximum Water Level Prediction in Beijing Mi-Huai-Shun Water Source Area

Sun Yili, Guo Xiaoguang, Yu Hongkun, Wei Ning, Zhen Zhen

2022, 36(4): 295-300. doi: 10.3969/j.issn.1007-2993.2022.04.007

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By analyzing the variation and influencing factors of groundwater level, the dynamic characteristics of groundwater level in a single aquifer structure area in Miyun, Huairou and Shunyi in Beijing are divided into four stages: groundwater balance period (1960s—late 1970s), groundwater overexploitation period (1980s—2003), Huairou emergency water source impact period (2003—2015) and ecological water replenishment impact period (2015 to now). The exploitation of regional groundwater and ecological water replenishment are the main factors causing the change of regional water level. The change of groundwater level has the typical characteristics of artificial influence. In the future, with the water sources such as No. 8 water plant entering the production limit period, Huairou emergency water source entering the hot standby conservation period and the normalization of ecological water replenishment, the groundwater level will continue to rise rapidly because the aquifer structure in this area is mainly gravel and has great permeability. Based on the water level observation data of different time series in the study area, the maximum water level of Miyun, Huairou and Shunyi water source is predicted by quantitative analysis method. The research results can provide guidance and reference for the reasonable determination of anti-floating water level and groundwater control of deep foundation pit engineering in this area.

Design and Implementation of Immovable Cultural Relics Display System

Du Wenxiao, Sun Yuanping, Chen Lei, Chen Zhen, Li Shifeng

2022, 36(4): 301-304. doi: 10.3969/j.issn.1007-2993.2022.04.008

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As an important cultural heritage in China, immovable cultural relics have been damaged to varying degrees due to wind and rain erosion all the year around, and some of them have been damaged. Therefore, it is of great significance to display, publicize and promote the geographical information of each cultural heritage protection unit in digital form. The PC terminal and mobile terminal of immovable cultural relics display system were developed respectively based on SuperMap and Vue. Different types of cultural relics information could be displayed on a digital image map with unified geographic space and scale standard, which could be an advanced means of cultural relic publicity, promotion and protection. This system could provide credible data support for the cultural relics management department, and could also help the public to understand the history of national cultural relics and provide convenience for travel.

Discussion on Design Method of Single Point Pile-anchor Supporting Structure

Xu Kunkun, Zhu Yanzhi, Jiu Yongzhi, Qi Chunwei

2022, 36(4): 305-310. doi: 10.3969/j.issn.1007-2993.2022.04.009

[Abstract](145) [FullText HTML] (34) [PDF 1403KB](41)

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In order to optimize the design of single-point pile-anchor support for deep foundation pit, both safety reliability and economic rationality should be guaranteed. Based on an engineering example, static equilibrium method, equivalent beam method, elastic fulcrum method and finite element method were used respectively to calculate the internal force, displacement, minimum soil depth, anchorage force and ground settlement around the foundation pit. The results show that: the internal force of supporting pile calculated by static equilibrium method and equivalent beam method is the largest, then elastic fulcrum method, and smallest by finite element method. In the displacement analysis of the supporting pile, the elastic fulcrum method is used to simulate the deformation of the supporting structure, but the finite element method is more in line with the actual deformation of the supporting pile. As for surface settlement, the results calculated by "m" method are basically consistent with the results of finite element analysis.

Application of Grouting Filling Technology in Foundation Treatment of Goaf

Jin Bao, Cai Guanjun, Yan Fei

2022, 36(4): 311-316. doi: 10.3969/j.issn.1007-2993.2022.04.010

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With the continuous promotion of urbanization and the in-depth development of urban construction, the demand for development and construction in goaf is increasing. The concealment and uncertainty of goaf treatment are analyzed from the aspects of the distribution of goaf, the comparison and selection of treatment schemes, and the treatment of key construction problems through an engineering example of grouting filling in a goaf. A variety of physical detection methods, such as multi-channel transient surface wave test and wave velocity test, were comprehensively used, and goaf filling treatment effect was evaluated combining with drilling and coring, settlement monitoring and other means. The results show that the grouting filling is effective and meets the design requirements, which can provide a reference for the grouting filling treatment project in goaf.

Detection and Adjustment of Gross Errors In Survey Data

Chen Lei, Yao Peijun, Sun Yuanping, Wang Lan

2022, 36(4): 317-322. doi: 10.3969/j.issn.1007-2993.2022.04.011

[Abstract](246) [FullText HTML] (36) [PDF 547KB](37)

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Baarda's traditional gross error test method was used to test and eliminate the gross errors in the data. The data with gross errors were processed by robust estimation method and traditional adjustment method respectively, and the results were compared with those before adding gross errors. The advantages and disadvantages of different gross error processing methods were compared. It is concluded that under the condition of ensuring a certain number of iterative calculations, robust estimation can achieve the purpose of resisting gross errors. Compared with robust estimation, Baarda gross error detection can ensure the calculation efficiency on the premise of meeting certain accuracy requirements when there is only one gross error in the data. When the data contains multiple gross errors, the robust estimation method can be used for processing.

Study on Stability of Advance Self-propelled Anchor Rod for Fault Breccia Tunnel

Wang Yan, Ren Dongwei, Li Tao, Chen Daikun

2022, 36(4): 323-328. doi: 10.3969/j.issn.1007-2993.2022.04.012

[Abstract](42) [FullText HTML] (11) [PDF 1973KB](14)

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For heavily weathered fault breccia tunnel, advance support is prone to problems such as jamming and difficulty in forming holes, and tunnel excavation can easily cause tunnel face collapse, resulting in safety hazards. In order to solve the problem of advance construction in fault breccia tunnel, a successful application of self-propelled hollow grouting anchor rod advanced construction technology in Beijing Yudushan Tunnel was introduced, and the advantages of self-propelled hollow grouting anchor rod as advanced support in fault breccia tunnel instead of ordinary advanced small conduits was analyzed. It is concluded that a reasonable increase in the initial support strength of the fault breccia tunnel can inhibit the expansion of the plastic zone of the tunnel surrounding rock to enhance the stability of the surrounding rock. Combined with the field situation, the mechanical model of fault breccia tunnel was established to analyze the plastic zone of surrounding rock. The reasonable support parameters and grouting pressure for the self-propelled anchor rod were determined by test comparison. The reasonableness of these parameters was also verified based on the effect of the advanced support after excavation of the tunnel face, which provides a reference for similar strata.

Application of Glass Fiber Reinforced Bar Anchor in Foundation Pit Engineering

Wang Wei, Wang Haicheng, Liu Zhiping

2022, 36(4): 329-333. doi: 10.3969/j.issn.1007-2993.2022.04.013

[Abstract](156) [FullText HTML] (34) [PDF 1929KB](34)

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The application of glass fiber reinforced bar as anchor rod body in foundation pit engineering is introduced through engineering examples. The use of glass fiber reinforced bar instead of ordinary reinforced anchor rod or steel strand anchor cable effectively solves the problem that the rigid structure cannot go out of the red line of land and become a permanent ground barrier. Although the tensile strength of glass fiber reinforced bar is higher than that of ordinary steel bar, there are still some problems in the technical links such as the connection of bar body and the tension of glass fiber reinforced bar anchor, resulting in the tensile performance of fiberglass reinforcement can not be brought into full play. The fully bonded glass fiber anchor is directly cast into the crown beam (waist beam) without prestress, which avoids the disadvantage of low tensile force of the anchor due to the glass fiber connection. With the special connector at the end of glass fiber reinforced bar converted to steel strand, the tensioning of glass fiber reinforced bar anchor bar can be realized.

Design and Application of Top-down Construction Method Pier Type Retaining Wall in Soil-rock Combined Deep Foundation Pit Support

Deng Chao, Du Yingping, Tian Pengfei

2022, 36(4): 334-339. doi: 10.3969/j.issn.1007-2993.2022.04.014

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In the floodplain area of mountainous areas, the upper soil layer is relatively thin and low in strength, while the underlying bedrock has high strength, thick thickness and stable distribution. Excavation of deep foundation pits under such geological conditions, when the surrounding environment of the foundation pit is complicated and the space for grading is limited, it is difficult and expensive to use the traditional pile row system to construct; and the supporting system of "hanging foot pile" with shallow embedded depth often loses its applicability due to the blocking of anchor pulling in the middle and upper part of the pile. In order to solve the above problems, combining the experience of deep foundation pit support combined with soil and rock in northwest Hubei, a design and construction method of top-down pier type retaining wall support is proposed. The engineering practice shows that the calculation theory of the top-down pier type retaining wall is clear, and it has obvious advantages such as convenient construction and economical cost. Relevant results can provide important technical reference for similar deep foundation pit engineering.

Comparative Study on Creep Characteristics of Fine Coral Sand, Quartz Sand and Cohesive Soil

Li Jianguang, Zhang Qichang, Wang Duli, Wang Lu, Liu Shaobo

2022, 36(4): 340-344. doi: 10.3969/j.issn.1007-2993.2022.04.015

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The hydraulic fill foundation for coral sand is mainly composed of coral sand, coral branches and reef limestone fragments, which are dredged by trailing suction or cutter suction. The coral sand particles are uneven in size and irregular in distribution, with edges and internal pores. The long-term slow deformation of coral sand foundation is the key point of deformation control of buildings. Through the creep test indoor in 135 days, the creep characteristics of fine coral sand, quartz sand and cohesive soil are compared and analyzed. It is found that the creep characteristics of fine coral sand and quartz sand are similar, and they are obviously different from cohesive soil. Under lower load level, the long-term deformation of fine coral sand foundation can be estimated based on the conclusions from quartz sand.

2022 Vol. 36, No. 4